A voice message, or “voice mail,” system (VMS) is typically implemented in a centralized server in commercial mobile telephony networks. In such networks, the network components, such as Mobile Switching Center (MSC), Short Message Service Center (SMS-C) and Radio Access Network (RAN) subsystems, are typically physically-connected to form a network that can cover vast geographical areas. For military, civil defense or disaster recovery operations, however, it is advantageous to deploy many portable, independent, “network-in-a-box,” systems which each contain a RAN as well as the core network components. Such a scaled-down system, also referred to as a Compact System, is capable of providing service to mobile stations within its radio coverage area without being dependent on physical connectivity to any other telecommunications infrastructure; the system is completely self-contained and is capable of stand-alone operation.
In a deployment scenario with independent mobile systems that are either physically-mobile or are stationary but deployed in remote areas with intermittent satellite or microwave links, a centralized VMS may not be accessible all the time. Furthermore, if a centralized VMS is relied upon, it becomes a single-point of failure. Thus, in such scenarios, it would be advantageous to have a distributed VMS solution that can provide voice mail service to mobile stations even if the serving independent mobile system is operating in stand-alone mode. Accordingly, there is a need in the art for improved apparatus and methods for providing voice message services to a user of a mobile terminal in a communications network having independent mobile telephony systems. Preferably, such improved apparatus and methods will provide fault-tolerance to allow for continued VMS services throughout the communications network if a single VMS should fail.